Update the intrinsic checker tool

[Amanieu]

This PR does several things:

• The intrinsics are now checked against Clang 13, which matches the version of LLVM currently used by rustc.
• The intrinsic checker is extended to also check 32-bit ARM intrinsics.
• missing_arm.txt and missing_aarch64.txt are updated to list all missing intrinsics from Clang & stdarch.

cc @JamieCunliffe @SparrowLii

[rust-highfive]

@Amanieu: no appropriate reviewer found, use r? to override